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De Zoysa T, Hauke AC, Iyer NR, Marcus E, Ostrowski SM, Stegemann F, Ermolenko DN, Fay JC, Phizicky EM. A connection between the ribosome and two S. pombe tRNA modification mutants subject to rapid tRNA decay. PLoS Genet 2024; 20:e1011146. [PMID: 38295128 PMCID: PMC10861057 DOI: 10.1371/journal.pgen.1011146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 02/12/2024] [Accepted: 01/22/2024] [Indexed: 02/02/2024] Open
Abstract
tRNA modifications are crucial in all organisms to ensure tRNA folding and stability, and accurate translation. In both the yeast Saccharomyces cerevisiae and the evolutionarily distant yeast Schizosaccharomyces pombe, mutants lacking certain tRNA body modifications (outside the anticodon loop) are temperature sensitive due to rapid tRNA decay (RTD) of a subset of hypomodified tRNAs. Here we show that for each of two S. pombe mutants subject to RTD, mutations in ribosomal protein genes suppress the temperature sensitivity without altering tRNA levels. Prior work showed that S. pombe trm8Δ mutants, lacking 7-methylguanosine, were temperature sensitive due to RTD, and that one class of suppressors had mutations in the general amino acid control (GAAC) pathway, which was activated concomitant with RTD, resulting in further tRNA loss. We now find that another class of S. pombe trm8Δ suppressors have mutations in rpl genes, encoding 60S subunit proteins, and that suppression occurs with minimal restoration of tRNA levels and reduced GAAC activation. Furthermore, trm8Δ suppression extends to other mutations in the large or small ribosomal subunit. We also find that S. pombe tan1Δ mutants, lacking 4-acetylcytidine, are temperature sensitive due to RTD, that one class of suppressors have rpl mutations, associated with minimal restoration of tRNA levels, and that suppression extends to other rpl and rps mutations. However, although S. pombe tan1Δ temperature sensitivity is associated with some GAAC activation, suppression by an rpl mutation only modestly inhibits GAAC activation. We propose a model in which ribosomal protein mutations result in reduced ribosome concentrations, leading to both reduced ribosome collisions and a reduced requirement for tRNA, with these effects having different relative importance in trm8Δ and tan1Δ mutants. This model is consistent with our results in S. cerevisiae trm8Δ trm4Δ mutants, known to undergo RTD, fueling speculation that this model applies across eukaryotes.
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Affiliation(s)
- Thareendra De Zoysa
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Alayna C. Hauke
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Nivedita R. Iyer
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Erin Marcus
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Sarah M. Ostrowski
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Franziska Stegemann
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Dmitri N. Ermolenko
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
| | - Justin C. Fay
- Department of Biology, University of Rochester, Rochester, New York, United States of America
| | - Eric M. Phizicky
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York, United States of America
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2
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Davey-Young J, Hasan F, Tennakoon R, Rozik P, Moore H, Hall P, Cozma E, Genereaux J, Hoffman KS, Chan PP, Lowe TM, Brandl CJ, O’Donoghue P. Mistranslating the genetic code with leucine in yeast and mammalian cells. RNA Biol 2024; 21:1-23. [PMID: 38629491 PMCID: PMC11028032 DOI: 10.1080/15476286.2024.2340297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/03/2024] [Indexed: 04/19/2024] Open
Abstract
Translation fidelity relies on accurate aminoacylation of transfer RNAs (tRNAs) by aminoacyl-tRNA synthetases (AARSs). AARSs specific for alanine (Ala), leucine (Leu), serine, and pyrrolysine do not recognize the anticodon bases. Single nucleotide anticodon variants in their cognate tRNAs can lead to mistranslation. Human genomes include both rare and more common mistranslating tRNA variants. We investigated three rare human tRNALeu variants that mis-incorporate Leu at phenylalanine or tryptophan codons. Expression of each tRNALeu anticodon variant in neuroblastoma cells caused defects in fluorescent protein production without significantly increased cytotoxicity under normal conditions or in the context of proteasome inhibition. Using tRNA sequencing and mass spectrometry we confirmed that each tRNALeu variant was expressed and generated mistranslation with Leu. To probe the flexibility of the entire genetic code towards Leu mis-incorporation, we created 64 yeast strains to express all possible tRNALeu anticodon variants in a doxycycline-inducible system. While some variants showed mild or no growth defects, many anticodon variants, enriched with G/C at positions 35 and 36, including those replacing Leu for proline, arginine, alanine, or glycine, caused dramatic reductions in growth. Differential phenotypic defects were observed for tRNALeu mutants with synonymous anticodons and for different tRNALeu isoacceptors with the same anticodon. A comparison to tRNAAla anticodon variants demonstrates that Ala mis-incorporation is more tolerable than Leu at nearly every codon. The data show that the nature of the amino acid substitution, the tRNA gene, and the anticodon are each important factors that influence the ability of cells to tolerate mistranslating tRNAs.
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Affiliation(s)
- Josephine Davey-Young
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Farah Hasan
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Rasangi Tennakoon
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Peter Rozik
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Henry Moore
- Department of Biomolecular Engineering, Baskin School of Engineering & UCSC Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Peter Hall
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Ecaterina Cozma
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Julie Genereaux
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | | | - Patricia P. Chan
- Department of Biomolecular Engineering, Baskin School of Engineering & UCSC Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Todd M. Lowe
- Department of Biomolecular Engineering, Baskin School of Engineering & UCSC Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Christopher J. Brandl
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
| | - Patrick O’Donoghue
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada
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3
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De Zoysa T, Hauke AC, Iyer NR, Marcus E, Ostrowski SM, Fay JC, Phizicky EM. A connection between the ribosome and two S. pombe tRNA modification mutants subject to rapid tRNA decay. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.18.558340. [PMID: 37790432 PMCID: PMC10542129 DOI: 10.1101/2023.09.18.558340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/05/2023]
Abstract
tRNA modifications are crucial in all organisms to ensure tRNA folding and stability, and accurate translation in the ribosome. In both the yeast Saccharomyces cerevisiae and the evolutionarily distant yeast Schizosaccharomyces pombe, mutants lacking certain tRNA body modifications (outside the anticodon loop) are temperature sensitive due to rapid tRNA decay (RTD) of a subset of hypomodified tRNAs. Here we show that for each of two S. pombe mutants subject to RTD, mutations in ribosomal protein genes suppress the temperature sensitivity without altering tRNA levels. Prior work showed that S. pombe trm8Δ mutants, lacking 7-methylguanosine, were temperature sensitive due to RTD and that one class of suppressors had mutations in the general amino acid control (GAAC) pathway, which was activated concomitant with RTD, resulting in further tRNA loss. We now find that another class of S. pombe trm8Δ suppressors have mutations in rpl genes, encoding 60S subunit proteins, and that suppression occurs with minimal restoration of tRNA levels and reduced GAAC activation. Furthermore, trm8Δ suppression extends to other mutations in the large or small ribosomal subunit. We also find that S. pombe tan1Δ mutants, lacking 4-acetylcytidine, are temperature sensitive due to RTD, that one class of suppressors have rpl mutations, associated with minimal restoration of tRNA levels, and that suppression extends to other rpl and rps mutations. However, although S. pombe tan1Δ temperature sensitivity is associated with some GAAC activation, suppression by an rpl mutation does not significantly inhibit GAAC activation. These results suggest that ribosomal protein mutations suppress the temperature sensitivity of S. pombe trm8Δ and tan1Δ mutants due to reduced ribosome concentrations, leading to both a reduced requirement for tRNA, and reduced ribosome collisions and GAAC activation. Results with S. cerevisiae trm8Δ trm4Δ mutants are consistent with this model, and fuel speculation that similar results will apply across eukaryotes.
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Affiliation(s)
- Thareendra De Zoysa
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
| | - Alayna C. Hauke
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
| | - Nivedita R. Iyer
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
| | - Erin Marcus
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
| | - Sarah M. Ostrowski
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
| | - Justin C. Fay
- Department of Biology, University of Rochester, Rochester, NY, USA 14627
| | - Eric M. Phizicky
- Department of Biochemistry and Biophysics, Center for RNA Biology, University of Rochester School of Medicine, Rochester, NY, USA 14642
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4
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Preston MA, Phizicky EM. The requirement for the highly conserved G-1 residue of Saccharomyces cerevisiae tRNAHis can be circumvented by overexpression of tRNAHis and its synthetase. RNA (NEW YORK, N.Y.) 2010; 16:1068-77. [PMID: 20360392 PMCID: PMC2856879 DOI: 10.1261/rna.2087510] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Accepted: 02/12/2010] [Indexed: 05/23/2023]
Abstract
Nearly all tRNA(His) species have an additional 5' guanine nucleotide (G(-1)). G(-1) is encoded opposite C(73) in nearly all prokaryotes and in some archaea, and is added post-transcriptionally by tRNA(His) guanylyltransferase (Thg1) opposite A(73) in eukaryotes, and opposite C(73) in other archaea. These divergent mechanisms of G(-1) conservation suggest that G(-1) might have an important cellular role, distinct from its role in tRNA(His) charging. Thg1 is also highly conserved and is essential in the yeast Saccharomyces cerevisiae. However, the essential roles of Thg1 are unclear since Thg1 also interacts with Orc2 of the origin recognition complex, is implicated in the cell cycle, and catalyzes an unusual template-dependent 3'-5' (reverse) polymerization in vitro at the 5' end of activated tRNAs. Here we show that thg1-Delta strains are viable, but only if histidyl-tRNA synthetase and tRNA(His) are overproduced, demonstrating that the only essential role of Thg1 is its G(-1) addition activity. Since these thg1-Delta strains have severe growth defects if cytoplasmic tRNA(His) A(73) is overexpressed, and distinct, but milder growth defects, if tRNA(His) C(73) is overexpressed, these results show that the tRNA(His) G(-1) residue is important, but not absolutely essential, despite its widespread conservation. We also show that Thg1 catalyzes 3'-5' polymerization in vivo on tRNA(His) C(73), but not on tRNA(His) A(73), demonstrating that the 3'-5' polymerase activity is pronounced enough to have a biological role, and suggesting that eukaryotes may have evolved to have cytoplasmic tRNA(His) with A(73), rather than C(73), to prevent the possibility of 3'-5' polymerization.
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MESH Headings
- Base Sequence
- Conserved Sequence
- Gene Expression
- Genes, Fungal
- Histidine-tRNA Ligase/genetics
- Histidine-tRNA Ligase/metabolism
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- Nucleotidyltransferases/genetics
- Nucleotidyltransferases/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Transfer, His/chemistry
- RNA, Transfer, His/genetics
- RNA, Transfer, His/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
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Affiliation(s)
- Melanie A Preston
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
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5
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Abstract
Recently, a general method was developed that makes it possible to genetically encode unnatural amino acids with diverse physical, chemical, or biological properties in Escherichia coli, yeast, and mammalian cells. More than 30 unnatural amino acids have been incorporated into proteins with high fidelity and efficiency by means of a unique codon and corresponding tRNA/aminoacyl-tRNA synthetase pair. These include fluorescent, glycosylated, metal-ion-binding, and redox-active amino acids, as well as amino acids with unique chemical and photochemical reactivity. This methodology provides a powerful tool both for exploring protein structure and function in vitro and in vivo and for generating proteins with new or enhanced properties.
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Affiliation(s)
- Lei Wang
- The Jack H. Skirball Center for Chemical Biology & Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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6
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7
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Abstract
Although chemists can synthesize virtually any small organic molecule, our ability to rationally manipulate the structures of proteins is quite limited, despite their involvement in virtually every life process. For most proteins, modifications are largely restricted to substitutions among the common 20 amino acids. Herein we describe recent advances that make it possible to add new building blocks to the genetic codes of both prokaryotic and eukaryotic organisms. Over 30 novel amino acids have been genetically encoded in response to unique triplet and quadruplet codons including fluorescent, photoreactive, and redox-active amino acids, glycosylated amino acids, and amino acids with keto, azido, acetylenic, and heavy-atom-containing side chains. By removing the limitations imposed by the existing 20 amino acid code, it should be possible to generate proteins and perhaps entire organisms with new or enhanced properties.
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Affiliation(s)
- Lei Wang
- Department of Pharmacology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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8
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Koyama H, Ito T, Nakanishi T, Kawamura N, Sekimizu K. Transcription elongation factor S-II maintains transcriptional fidelity and confers oxidative stress resistance. Genes Cells 2004; 8:779-88. [PMID: 14531857 DOI: 10.1046/j.1365-2443.2003.00677.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND During transcription elongation, RNA polymerase II is arrested on the template when incorrect ribonucleotides are incorporated into the nascent transcripts. Transcription factor S-II enhances the excision of these mis-incorporated nucleotides by RNA polymerase II and stimulates transcription elongation in vitro. This mechanism is considered to be transcriptional proof-reading, but its physiological relevance remains unknown. RESULTS We report that S-II contributes to the maintenance of transcriptional fidelity in vivo. We employed a genetic reporter assay utilizing a mutated lacZ gene from which active beta-galactosidase protein is expressed when mRNA proof-reading is compromised. In S-II-disrupted mutant yeasts, beta-galactosidase activity was ninefold higher than that in wild-type. The S-II mutant exhibited sensitivity to oxidants, which was suppressed by introduction of the S-II gene. The mutant S-II proteins, which are unable to stimulate transcription by RNA polymerase II in vitro, did not suppress the sensitivity of the mutants to oxidative stress or maintain transcriptional fidelity. CONCLUSION These results suggest that S-II confers oxidative stress resistance by providing an mRNA proof-reading mechanism during transcription elongation.
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Affiliation(s)
- Hiroshi Koyama
- Department of Developmental Biochemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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9
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Atkin AL, Riazi MA, Greer CL, Roy KL, Bell JB. The functional analysis of nonsense suppressors derived from in vitro engineered Saccharomyces cerevisiae tRNA(Trp) genes. Gene 1993; 134:57-65. [PMID: 8244031 DOI: 10.1016/0378-1119(93)90174-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Nonsense suppressors derived from Saccharomyces cerevisiae tRNA(Trp) genes have not been identified by classical genetic screens, although one can construct efficient amber (am) suppressors from them by making the appropriate anticodon mutation in vitro. Herein, a series of in vitro constructed putative suppressor genes was produced to test if pre-tRNA(Trp) processing difficulties could help to explain the lack of classical tRNA(Trp)-based suppressors. It is clear that inefficient processing of introns from precursor tRNA(Trp), or inaccurate overall processing, may explain why some of these constructs fail to promote nonsense suppression in vivo. However, deficient processing must be only one of the reasons why classical tRNA(Trp)-based suppressors have not been characterized, as suppression may still be extremely weak or absent in instances where the in vitro construct can lead to an accumulation of mature tRNA(Trp). Furthermore, suppression is also very weak in strains transformed with an intronless derivative of a putative tRNA(Trp) ochre (oc) suppressor gene, wherein intron removal cannot pose a problem.
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MESH Headings
- Base Sequence
- Blotting, Northern
- Genes, Fungal
- Genes, Suppressor
- Introns
- Molecular Sequence Data
- Nucleic Acid Conformation
- Phenotype
- RNA Processing, Post-Transcriptional
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Messenger/metabolism
- RNA, Transfer, Trp/chemistry
- RNA, Transfer, Trp/genetics
- Saccharomyces cerevisiae/genetics
- Transformation, Genetic
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Affiliation(s)
- A L Atkin
- Department of Genetics, University of Alberta, Edmonton, Canada
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10
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Carneiro VT, Pelletier G, Small I. Transfer RNA-mediated suppression of stop codons in protoplasts and transgenic plants. PLANT MOLECULAR BIOLOGY 1993; 22:681-90. [PMID: 8343603 DOI: 10.1007/bf00047408] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have developed a simple, rapid and sensitive assay for tRNA gene expression in plant cells. A plant tRNA(Leu) gene was site-specifically mutated to encode each of the three anticodon sequences (CUA, UUA and UCA) that recognize, respectively, the amber, ochre and opal stop codons. The suppression activity of these genes was detected by their ability to restore transient beta-glucuronidase (GUS) expression in tobacco protoplasts electroporated with GUS genes containing premature stop codons. Protoplasts co-electroporated with the amber suppressor tRNA gene and a GUS gene containing a premature amber stop codon showed up to 20-25% of the activity found in protoplasts transfected with the functional control GUS gene. Ochre and opal suppressors presented maximum efficiencies of less than 1%. This system could be adapted to examine transcription, processing or aminoacylation of tRNAs in plant cells. In addition, phenotypically normal, fertile tobacco plants expressing a stably incorporated amber suppressor tRNA gene have been obtained. This suppressor tRNA can be used to transactivate a target gene containing a premature amber stop codon by a factor of at least several hundred-fold.
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MESH Headings
- Amino Acid Sequence
- Anticodon/genetics
- Base Sequence
- Codon/genetics
- Fabaceae/genetics
- Glucuronidase/genetics
- Kanamycin Resistance/genetics
- Molecular Sequence Data
- Mutation
- Peptide Chain Termination, Translational/genetics
- Plants, Genetically Modified/genetics
- Plants, Medicinal
- Plants, Toxic
- Protoplasts
- RNA, Transfer, Leu/biosynthesis
- RNA, Transfer, Leu/genetics
- Suppression, Genetic
- Nicotiana/genetics
- Transformation, Genetic
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Affiliation(s)
- V T Carneiro
- Laboratoire de Biologie Cellulaire, INRA, Versailles, France
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11
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Yesland K, Nelson A, Six Feathers D, Johnson J. Identity of Saccharomyces cerevisiae tRNA(Trp) is not changed by an anticodon mutation that creates an amber suppressor. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)54137-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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12
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Atkin AL, Henry RW, Roy KL, Bell JB. Characterization of the tRNA(Trp) genes of Saccharomyces cerevisiae. Gene X 1992; 119:57-63. [PMID: 1398091 DOI: 10.1016/0378-1119(92)90066-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The purpose of this work was to examine the tRNA(Trp)-encoding genes (tRNA(Trp)) of Saccharomyces cerevisiae to gain insight as to why tRNA(Trp) amber suppressors, isolated by conventional genetic techniques, have not been reported. The results herein indicate that the haploid yeast genome contains six tRNA(Trp) genes which map to five or six chromosomes. Not only do the six genes have identical coding sequences but their introns are also identical. Gene replacement experiments indicate that five copies of tRNA(Trp) are sufficient for cell viability. Thus, mutation of one tRNA(Trp) gene to a suppressor in vivo, lowering the functional number of tRNA(Trp) genes, would not be expected to be lethal.
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Affiliation(s)
- A L Atkin
- Department of Genetics, University of Alberta, Edmonton, Canada
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13
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Yesland K, Kim D, Johnson JD. Copy number and chromosomal location of Saccharomyces cerevisiae tRNA(Trp)-encoding genes. Gene 1991; 99:137-8. [PMID: 2022321 DOI: 10.1016/0378-1119(91)90046-e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Yeast tRNA(Trp)-encoding genes have been identified by Southern-blot analysis of chromosomal DNA. Seven copies of this gene are detected in blots of both restriction endonuclease digests and intact chromosomal DNA. Electrophoretic mapping of tDNA(Trp) indicates one copy is located on each of chromosomes X, XI, XIII, and XVI. The remaining three copies are localized to chromosomes VII and/or XV. Three different yeast strains gave identical results indicating this multi-gene family is relatively stable.
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Affiliation(s)
- K Yesland
- Department of Molecular Biology, University of Wyoming, Laramie 82071
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14
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Dingermann T, Reindl N, Brechner T, Werner H, Nerke K. Nonsense suppression in Dictyostelium discoideum. DEVELOPMENTAL GENETICS 1990; 11:410-7. [PMID: 2096017 DOI: 10.1002/dvg.1020110514] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We describe the generation of Dictyostelium discoideum cell lines that carry different suppressor tRNA genes. These genes were constructed by primer-directed mutagenesis changing a tRNA(Trp)(CCA) gene from D. discoideum to a tRNA(Trp)(amber) gene and changing a tRNA(Glu)(UUC) gene from D. discoideum to a tRNA(Glu)(ochre) as well as a tRNA(Glu)(amber) gene. These genes were stably integrated into the D. discoideum genome together with a reporter gene. An actin 6::lacZ gene fusion carrying corresponding translational stop signals served as a reported. Active beta-galactosidase is expressed only in D. discoideum strains that contain, in addition to the reporter, a functional suppressor tRNA. Both amber suppressors are active in D. discoideum without interfering significantly with cell growth and development. We failed, however, to establish cell lines containing a functional tRNA(Glu)(ochre) suppressor. This may be due to the fact that nearly every message from D. discoideum known so far terminates with UAA. Therefore a tRNA capable of reading this termination codon may not be compatible with cell growth.
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MESH Headings
- Base Sequence
- Blotting, Northern
- Blotting, Southern
- Dictyostelium/genetics
- Electrophoresis, Polyacrylamide Gel
- Gene Expression Regulation, Fungal
- Genes, Fungal
- Genes, Lethal
- Genes, Suppressor
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Nucleic Acid Hybridization
- Phenotype
- Plasmids
- RNA, Transfer, Trp/genetics
- Saccharomyces cerevisiae/genetics
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Affiliation(s)
- T Dingermann
- Institut für Biochemie der Medizinischen Fakultät, Universität Erlangen-Nürnberg, Federal Republic of Germany
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